For the purpose of causing silver halide photographic materials to absorb light at particular wavelengths, the photographic emulsion or the other hydrophilic colloid layers of such materials are often colored.
When it becomes necessary to control the spectral composition of light incident upon a photographic emulsion layer, the photographic emulsion layer is generally provided with a colored layer on the side farther from the support. Such a colored layer is called a filter layer. In cases where a plurality of photographic emulsion layers are present, any two of them may have a filter layer between them.
It is desirable to prevent images from being blurred (that is to say, to prevent halation from occurring), which is due to (i) scattering of light upon passage through photographic emulsion layers or after transmission thereby, (ii) reflection of the scattered light at the interface of the emulsion layer and the support or by the surface of the photographic material situated in the position opposite to the emulsion layer side, and (iii) re-incidence of the reflected light on the photographic emulsion layer. To do this, a colored layer called an anti-halation layer is formed between the photographic emulsion layer and the support, or on the back side of the support (which is opposite to the emulsion layer side). In cases where a plurality of photographic emulsion layers are present, an antihalation layer may be sandwiched between any two of them. In order to prevent image sharpness from lowering because of the scattering of light inside the photographic emulsion layers (this phenomenon is generally called irradiation), one can also color the photographic emulsion layers.
Usually dyes are incorporated into the hydrophilic colloid layers to be colored. It is required that such dyes satisfy the following requirements:
(1) their spectral absorption is proper for the end-use purpose;
(2) they are inert photochemically. That is, they do not have in a chemical sense any bad influence on the properties of the silver halide emulsion layers, such as lowering sensitivity, fading latent images, generation of fog, and so on;
(3) they are decolorized in the course of photographic processing, or eluted by a processing solution or washing water to leave no harmful influence on the photographic material after.the processing;
(4) they do not diffuse from the colored layer into other layers; and
(5) they have excellent storage stability in the form of solution or when they are incorporated into a photographic material, so that they cause neither color change nor fading upon storage.
In special cases where the colored layer is a filter layer or an antihalation layer disposed on the photographic emulsion layer side of a support, it is often necessary for these layers to be colored selectively and to be designed so that the coloring may not reach in a substantial sense into other layers. This is because the spread of coloring not only exerts a harmful influence on the spectral characteristics of the other layers but also spoils the function of the filter or antihalation layer. However, it frequently occurs that when the layer to which a dye is added and another hydrophilic colloid layer are brought into contact with each other in a wet condition, part of the dye diffuses from the former layer into the latter one. Many efforts, therefore, have been made to prevent such diffusion of the dye.
For instance, U.S. Pat. Nos. 2,548,564, 4,124,386 and 3,625,694 disclose a method in which a hydrophilic polymer bearing a positive charge is incorporated as a mordant into the layer containing a dissociated anionic dye to localize the dye to that layer through electrostatic interaction with the dye molecule.
In addition, a method of dyeing a particular layer with water-insoluble solid particles of a dye is disclosed in JP-A-56-12639 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-55-155350, JP-A-55-155351, JP-A-63-27838, JP-A-63-197943, European Patents 15,601, 274,723, 276,566 and 299,435, U.S. Pat. No. 4,803,150, WO 88/04794, and so on.
Moreover, a method of dyeing a particular layer with dye-adsorbed fine particles of a metal salt is disclosed in U.S. Pat. Nos. 2,719,088, 2,496,841 and 2,496,843, JP-A-60-45337, and so on.
However, when such improved methods are used, the speed of decolorization and/or elution of the dyes at the time of development is low, so that it is difficult to get rid of color stain arising from the dyes in cases where processing speed is increased, compositions of the processing solutions and those of the photographic emulsions are modified, and other factors are changed.